Electrons of mass m with de- Broglie wavelength λ fall on the target in an X-ray tube. The cut-off wavelength (λo) of the emitted X-ray is:

1.  λ0=2mcλ2h

2.  λ0=2hmc

3.  λ0=2m2c2λ2h2

4.  λ0=λ

Subtopic:  X-Ray (OLD NCERT) |
 55%
From NCERT
NEET - 2016
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If an electron in a hydrogen atom jumps from the \(3^{\text{rd}}\) orbit to the \(2^{\text{nd}}\) orbit, it emits a photon of wavelength \(\lambda\). When it jumps from the \(4^{\text{th}}\) orbit to the \(3^{\text{rd}}\) orbit, the corresponding wavelength of the photon will be:
1. \(\frac{16}{25}\lambda\) 2. \(\frac{9}{16}\lambda\)
3. \(\frac{20}{7}\lambda\) 4. \(\frac{20}{13}\lambda\)
Subtopic:  Bohr's Model of Atom |
 79%
From NCERT
NEET - 2016
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The ratio of wavelengths of the last line of the Balmer series and the last line of the Lyman series is:
1. \(1\)
2. \(4\)
3. \(0.5\)
4. \(2\)

Subtopic:  Spectral Series |
 77%
From NCERT
NEET - 2017
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The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom is:
1. \(1:1\)
2. \(1:-1\)
3. \(2:-1\)
4. \(1:-2\)

Subtopic:  Bohr's Model of Atom |
 80%
From NCERT
NEET - 2018
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Given that the value of the Rydberg constant is \(10^{7}~\text{m}^{-1},\) what will be the wave number of the last line of the Balmer series in the hydrogen spectrum?
1. \(0.5 \times 10^{7}~\text{m}^{-1}\)
2. \(0.25 \times 10^{7} ~\text{m}^{-1}\)
3. \(2.5 \times 10^{7}~\text{m}^{-1}\)
4. \(0.025 \times 10^{4} ~\text{m}^{-1}\)

Subtopic:  Spectral Series |
 86%
From NCERT
NEET - 2016
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When an \(\alpha\text-\)particle of mass \(m\) moving with velocity \(v\) bombards on a heavy nucleus of charge \(Ze\), its distance of closest approach from the nucleus depends on \(m\) as:
1. \(\frac{1}{\sqrt{m}}\)
2. \(\frac{1}{m^{2}}\)
3. \(m\)
4. \( \frac{1}{m}\)
Subtopic:  Various Atomic Models |
 75%
From NCERT
NEET - 2016
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In the spectrum of hydrogen, the ratio of the longest wavelength in the Lyman series to the longest wavelength in the Balmer series is:

1. \(\frac{4}{9}\) 2. \(\frac{9}{4}\)
3. \(\frac{27}{5}\) 4. \(\frac{5}{27}\)
Subtopic:  Spectral Series |
 70%
From NCERT
NEET - 2015
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Consider \(3^{\text{rd}}\) orbit of \(He^{+}\) (Helium). Using a non-relativistic approach, the speed of the electron in this orbit will be: (given \(Z=2\) and \(h\) (Planck's constant)\(= 6.6\times10^{-34}~\text{J-s}\))
1. \(2.92\times 10^{6}~\text{m/s}\)
2. \(1.46\times 10^{6}~\text{m/s}\)
3. \(0.73\times 10^{6}~\text{m/s}\)
4. \(3.0\times 10^{8}~\text{m/s}\)

Subtopic:  Bohr's Model of Atom |
 74%
From NCERT
NEET - 2015
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The ratio of the longest wavelengths corresponding to the Lyman and Balmer series in the hydrogen spectrum is:
1. \(\dfrac{3}{23}\) 2. \(\dfrac{7}{29}\)
3. \(\dfrac{9}{31}\) 4. \(\dfrac{5}{27}\)
Subtopic:  Spectral Series |
 88%
From NCERT
AIPMT - 2013
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An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be:
(\(m\) is the mass of hydrogen atom, \(R\) is Rydberg constant and \(h\) is Plank’s constant)
1. \(\frac{24m}{25hR}\)
2. \(\frac{25hR}{24m}\)
3. \(\frac{25m}{24hR}\)
4. \(\frac{24hR}{25m}\)

Subtopic:  Bohr's Model of Atom |
 60%
From NCERT
AIPMT - 2012
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